Circuit breaker and fuse interlock mechanism

ABSTRACT

An interlock mechanism between a circuit breaker and fuse element associated with a distribution transformer wherein, due to the interlock mechanism, the circuit breaker switch must be moved to a particular position in order to disengage a fuse cover assembly thereby permitting actuation of the fuse cover assembly to permit removal of the fuse element. The circuit breaker is adapted to be positioned in one of four positions, either the lines open, line A only, lines A and B, or line B only positions. The interlock mechanism includes a hinged interlock bar which is moved to a position permitting the removal of the fuse element after the circuit breaker has been moved to the lines open position. The circuit breaker cannot be moved to the closed position, either line A, lines A and B, or line B only, until such time as the interlock bar is moved back into position to preclude the removal or insertion of the fuse element in other than the line open position of the circuit breaker. The purpose of the foregoing abstract is to enable the Patent Office and the public generally, and especially the scientists, engineers or practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by claims, nor is it intended to be limiting as to the scope of the invention in any way.

l l CIRCUIT BREAKER AND FUSE INTERLOCK MECHANISM l75| Inventors: Alan L. Wilks; James D. Richerson:

M. Denton Cormany, all of Versailles. Ky.

[73] Assignee: Kuhlman Corporation, Troy Mich.

[22] Filed: Oct. 31, 1974 I21] Appl No; 519.686

[521 L18. Cl. 337/4; 337/3; 337/4U2 [51] Int. C13. HOlH 37/00 I58] Field of Search 300/321. 322. 327. 333;

[56] References Cited L'NITED STATES PATENTS 1.209.918 7/1940 Hammer! 337/4 X 1.147662 7/1941 Matthews 337/8 X 3391,63] 13/1945 Craig 337/4 X 3571x509 4/1971 Bernatt. 337/8 X 3.841.381 lit/1974 Bernatt 337/4 X [57] ABSTRACT An interlock mechanism between a circuit breaker 1 Sept. 30, 1975 and fuse element associated with a distribution trans former wherein. due to the interlock mechanism, the circuit breaker switch must be moved to a particular position in order to disengage a fuse cover assembly thereby permitting actuation ol the fuse cover assembly to permit removal of the fuse element.

The circuit breaker is adapted to be positioned in one of four positions. either the lines open. line A only, lines A and B. or line B only positions. The interlock mechanism includes a hinged interlock bar which is moved to a position permitting the removal of the fuse element after the circuit breaker has been moved to the lines open position. The circuit breaker cannot be moved to the closed position. either line A. lines A and B, or line B only until such time as the interlock bar is moved back into position to preclude the removal or insertion of the fuse element in other than the line open position 01' the circuit breaker.

The purpose of the foregoing abstract is to enable the Patent Office and the public generally. and especially the scientists. engineers or practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence oi the technical disclosure of the application. The abstract is neither intended to define the invention ot the application. which is measured by claims. nor is it intended to be limiting as to the scope of the invention in any way.

[0 Claims, 4 Drawing Figures CIRCUIT BREAKER AND FUSE INTERLOCK MECHANISM BACKGROUND AND SUMMARY OF THE DISCLOSURE This invention relates generally to an interlock mechanism for use with a circuit breaker and removable fuse element, and more particularly, to an interlock mechanism which includes a hinged interlock bar which precludes the removal of the fuse element until such time as the circuit breaker is moved to a circuit open position.

There has been a recent trend in the electrical distribution transformer field to move the distribution trans formers from overhead poles to underground type, buried wire distribution. With this evolvement, additional safety features are desired to be incorporated into the distribution transformer. One such safety feature is the provision of removable fuses which may readily be removed from the outside of the transformer housing to service the transformer and also to provide easy replacement of the fuse in the event of a circuit overload.

With the provision of this type of removable fuse, distribution transformers are being provided circuit breaker switches which are adapted to open circuit the electrical windings within the distribution transformer. In removing the fuse, it is desirable to disconnect the transformer from the source of supply by opening the circuit breaker prior to the removal of the fuse. This is true because of the fact that the removal of the fuse while the internal system is provided with electrical en ergy may cause an arcing as the fuse is removed thereby creating transients within the system which may cause the fuse to blow or cause internal damage within the apparatus which may also injure the operator. In those cases where a circuit breaker is provided in series with the fuse element, certain prior art systems do not require the circuit breaker switch to be operated prior to the removal of the fuse. In this situation, it is possible for the service personnel working on the electrical apparatus to forget to open the circuit breaker prior to the removal of the fuse resulting in the dangers described above, a blown fuse, damaged equipment or injuries to the service personnel. Accordingly, it has been found to improve safety by providing a circuit breaker in series with the fuse wherein the circuit breaker incorporates an interlock mechanism requiring that the circuit breaker switch be moved to the off position prior to permitting removal of the fuse.

The system of the present invention provides such an interlock mechanism whereby the circuit breaker must he moved from one of three circuit-on positions to a circuit-off position before the fuse is capable of being removed. The interlock mechanism incorporates a hinged interlock bar which cooperates with a cam plate attached to the shaft of a circuit breaker switch whereby the cam plate must be moved to a particular position to permit the interlock bar to be hingedly moved out of interference with the fuse assembly and its associated cover.

Accordingly, it is one object of the present invention to provide a combined fuse and circuit breaker interlock assembly for use in conjunction with electrical apparatus.

It is another object of the present invention to provide an improved interlock mechanism for use in condom .l

(ill

junction with a fuse and circuit breaker assembly which is particularly adapted for use in conjunction with transformer assemblies.

It is a further object of the present invention to provide an improved hinged interlock mechanism which is interfered with by a member associated with a circuit breaker wherein the circuit breaker must be moved to the off position prior to the movement of the interlock mechanism.

It is another object of the present invention to provide an interlock mechanism of the type described wherein the circuit breaker switch may not be moved to the circuit-on position while the interlock mechanism is open.

It is still a further object of the present invention to provide an improved interlock mechanism for use in conjunction with a fuse and circuit breaker assembly which is inexpensive to manufacture, easily installed and reliable in operation.

The invention to be protected will be particularly pointed out and distinctly claimed in the claims appended hereto. Further objects, features and advantages of the present invention will become more readily apparent from a detailed study of the specification, when taken in conjunction with the attached drawing, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a distribution transformer assembly, partially broken away, and particularly illustrating the interlock mechanism of the present invention;

FIG. 2 is a side view of FIG. I, and particularly illustrating the relationship of the interlock mechanism and the fuse assembly;

FIG. 3 is a front view of the transformer assembly of FIG. 1 with the cam plate moved into the close circuit position and interfering with the interlock bar; and

FIG. 4 is a front view of the transformer assembly of FIG. I and particularly illustrating the cam plate in the open circuit position with the hinged interlock bar moved out of interference with the fuse cover plate.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Referring now to the drawings, particularly to FIG. I thereof, there is illustrated a distribution transformer assembly 10 which is of the type presently being sold for use in conjunction with domestic distribution of electrical energy. Generally, the transformer assembly 10 includes a face plate I2, and frame assembly I4 which encloses the windings of the transformer. Also, the face plate 12 and frame assembly 14 encloses a circuit breaker assembly, the circuit breaker assembly being operated by means of a circuit breaker cam plate assembly I6. The cam plate assembly 16 is indicated as being adapted to be moved to four positions as indicated by the indicia noted on the face plate 12. For example, the cam plate assembly I6 as illustrated in FIG. I is shown in the circuit open position and the indicia further indicates that the cam plate assembly may be moved to a line B only position wherein the circuit breaker interconnects only line B of the transformer, the lines A and B position, wherein the circuit breaker is moved into a position such that lines A and B are interconnected to thereby close circuits A and B, and to a line A only position wherein only the A circuit is closed.

The distribution transformer further includes a fuse assembly 18 which includes a sleeve 20 mounted to the exterior of the plate 12, a fuse (not shown), and a fuse holder assembly (not shown). The interior of the sleeve 20 is adapted to receive the fuse holder assembly, and particularly the portion thereof shown as an expandable gasket lock assembly 22 which is adapted to frictionally engage the interior portion of the sleeve 20 to retain the expandable lock assembly 22 within sleeve 20. The assembly 22 is adapted to position the fuse element in the interior of the tank formed by frame assembly 14 and face plate 12 and into engagement with the winding circuit elements such that the fuse is properly positioned in circuit with the primary winding of the transformer mounted within the assembly 10.

As is particularly seen from FIG. 2, the plug mechanism 22 is actuated by means of a handle 24 which, when in the position shown in FIG. 2, expands a flexible gasket element into engagement with the interior of the sleeve 20. When it is desired to remove the lock assembly 22, and the associated fuse, the handle 24 is rotated from the position shown in a closkwise direction downwardly to a position generally parallel to the lower side 26 of the sleeve 20. The fuse is then removed by grasping the plug assembly 22.

However, as is best seen from FIG. 2, the handle 24 cannot be rotated a sufficient distance due to the fact that a hinged interlock bar mechanism 30, which includes a generally vertical portion 32, is positioned in interfering relation with the handle 24. Thus, with the hinged interlock mechanism 30 in the position shown, the handle 24 is precluded from being rotated in the clockwise direction as described above due to the proximity of the vertical portion 32 in the path of travel of handle 24.

The cam plate assembly 16 includes a cam plate 34, which cam plate 34 is generally circular with the exception that a portion adjacent edge 36 has been removed to form a flat. As seen from FIG. 2, the circular portion of the cam plate 34 is adapted to be positioned over, at an edge thereof, the lower end 38 of a hinged interlock bar 40. Thus, if the cam plate 34 is positioned in any position other than that shown in FIGS. 1, 2 and 4, for example, the position shown in FIG. 3, the outer edge of the cam plate 34 will interfere with the portion 38 of the hinge lock bar 40 forming a part of the hinge lock assembly 30. Thus, the bar 40 is precluded from being pivoted from the position shown in FIG. 1 to the position shown in FIG. 4, and it is impossible to rotate the handle 24 to remove the fuse associated with the lock mechanism 22.

In this way, the operator must move the cam plate 34, with the associated circuit breaker, from any of the positions wherein the circuit breaker has closed the circuit in either line A, line B, or lines A and B to the open position wherein the flat portion 36 is aligned with the edge of the portion 38. Thus, the fuse cannot be removed when the internal circuit for the transformer is completed.

On the other hand, if the bar 40 is in the open position as illustrated in FIG. 4, it is impossible to close the circuit breaker by rotating cam plate 34 because the lower edge 38 Of the hinged interlock bar 40 is a greater width than the distance between the face plate 12 and the cam plate 34. Accordingly, the bar 40 must be moved back into the closed position illustrated in FIG. 1 in order to reposition the circuit breaker to the closed circuit position. Thus, an operator is precluded from closing the circuit by rotating the cam plate 34 and thereafter inserting a fuse into the opening formed by the sleeve 20.

FIG. 3 illustrates the cam plate 34 in its closed position wherein the circuit breaker switch has closed the circuit to the transformer windings and the hinged interlock bar 40 is closed over the opening formed by the sleeve 20. As is seen from FIG. 3, a fuse holder assembly has been inserted into the opening formed by sleeve 20 and there is no possibility of moving the interlock bar 40 out of the way of the lock assembly 22 without first moving the cam plate 34 to the open position. The interlock bar 40 is mounted to the face plate 12 by means of a piano type hinge 42 and the circuit breaker assembly has been provided with a pointer element 44 to aid the service person in selecting one of the four positions for the circuit breaker assembly 16.

It is contemplated that the inventive concepts and principles herein disclosed may be variously otherwise embodied and it is intended that the appended claims cover alternative embodiments except insofar as limited by the prior art.

What is Claimed is:

1. In an electrical circuit, a circuit breaker interconnected in the electrical circuit to cut off the supply of energy from one portion of the circuit to another portion of the circuit, a removable overload responsive device interconnected in the another portion of the circuit, the improvement comprising selection means interconnected with the circuit breaker to select, when actuated, an open circuit position and at least one closed circuit position, an overload responsive device holder assembly including a cover assembly for positioning the overload responsive device, said cover assembly including means movable to remove the overload device from the circuit, and interlock means hingedly supported in position over said overload device cover in the closed position and rotatable away from said overload device cover in the open position to permit removal of the overload device in said open position, and means on said selection means to preclude rotation of said interlock means when said selection means is in said at least one closed circuit position.

2. The improvement of claim 1 wherein said interlock means is a bar extending between said overload element cover assembly and said selection means.

3. The improvement of claim 2 wherein said selector means includes a plate member movable to at least two positions, one of said positions causing said plate member to overlie said bar to preclude rotation of said bar.

4. The improvement of claim 3 wherein said cover assembly includes a lock member movable from a locked to an unlocked position, said interlock bar interferring with said lock member movement when said bar is in the closed position.

5. The improvement of claim 4 wherein said bar is hingedly mounted along a side edge thereof to permit rotational movement of at least a portion of said bar from a position overlying said lock member to a p0sition alongside said lock member.

6. The improvement of claim 5 wherein said plate member includes a cut-away portion, said cut-away portion permitting rotation of said bar when said plate member is moved to the open circuit position.

portion engages an edge of said bar member adjacent said end portion to preclude rotation of said plate member when said bar member is rotated to a position along side said cover assembly.

10. The improvement of claim 9 wherein said electrical circuit is a distribution transformer and said overload element is a fuse, said selector being movable among four positions, one of said positions being an open circuit position and three of said positions being closed circuit. 

1. In an electrical circuit, a circuit breaker interconnected in the electrical circuit to cut off the supply of energy from one portion of the circuit to another portion of the circuit, a removable overload responsive device interconnected in the another portion of the circuit, the improvement comprising selection means interconnected with the circuit breaker to select, when actuated, an open circuit position and at least one closed circuit position, an overload responsive device holder assembly including a cover assembly for positioning the overload responsive device, said cover assembly including means movable to remove the overload device from the circuit, and interlock means hingedly supported in position over said overload device cover in the closed position and rotatable away from said overload device cover in the open position to permit removal of the overload device in said open position, and means on said selection means to preclude rotation of said interlock means when said selection means is in said at least one closed circuit position.
 2. The improvement of claim 1 wherein said interlock means is a bar extending between said overload element cover assembly and said selection means.
 3. The improvement of claim 2 wherein said selector means includes a plate member movable to at least two positions, one of said positions causing said plate member to overlie said bar to preclude rotation of said bar.
 4. The improvement of claim 3 wherein said cover assembly includes a lock member movable from a locked to an unlocked position, said interlock bar interferring with said lock member movement when said bar is in the closed position.
 5. The improvement of claim 4 wherein said bar is hingedly mounted along a side edge thereof to permit rotational movement of at least a portion of said bar from a position overlying said lock member to a position alongside said lock member.
 6. The improvement of claim 5 wherein said plate member includes a cut-away portion, said cut-away portion permitting rotation of said bar when said plate member is moved to the open circuit position.
 7. The improvement of claim 6 wherein said bar member includes a portion which, when rotated to said position alongside said lock member, precludes movement of said plate member to the closed circuit position.
 8. The improvement of claim 7 wherein said plate member is formed as a circle with a chord portion removed, all positions of said circular plate overlying said end portion of said bar member and said chord portion causing no portion of said circular plate to overlie Said bar member.
 9. The improvement of claim 8 wherein said chord portion engages an edge of said bar member adjacent said end portion to preclude rotation of said plate member when said bar member is rotated to a position along side said cover assembly.
 10. The improvement of claim 9 wherein said electrical circuit is a distribution transformer and said overload element is a fuse, said selector being movable among four positions, one of said positions being an open circuit position and three of said positions being closed circuit. 